1. Field of the Invention
This invention relates to an accumulator power supply unit which independently controls the charging of the respective accumulator block, comprising electrical double layer capacitors and secondary batteries connected in series or in series-parallel and supplies a DC power to electrical parts connected outside of the accumulator power supply unit.
2. Description of Prior Art
Traditionally, when plural electric double layer capacitors connected in series are charged, charging voltage is supplied in series to charge all double layer capacitors simultaneously so as to equalize the charging voltage of the respective capacitor.
However, since characteristic of the capacitors is not uniform and a state of charge of the respective capacitors varies, the traditional series charging method causes increased irregularity in the charging voltage of the respective capacitor and generates a portion that exceeds the withstand voltage of the capacitors. Capacitors that exceed the withstand voltage due to the overcharge have a problem in that a decomposition of the electrolyte is accelerated resulting in deterioration of the capacitor performance and durability.
In order to avoid overcharging the respective capacitor exceeding the withstand voltage, the voltage across the respective capacitor is detected for the purpose of bypassing the electric current at an overcharged portion of the respective capacitor, thereby equalizing the charging voltage across each of the capacitors.
For that reason, the traditional charging method requires an electric current bypass circuit for actually bypassing the electric current with possible overcharge.
However, the above structure causes a problem of power loss in the electric current bypass circuit leaving some portions ineffectively consuming electricity.
An object of this invention is to provide an accumulator power supply unit technology which does not require an electric current bypass circuit and does not cause a problem of unnecessary power loss when charging an accumulator block such as electric double layer capacitors and secondary batteries are connected in series or in series-parallel. Further, another object of this invention to provide an accumulator power supply unit technology which equalizes the voltage of the respective accumulator block regardless of the different increasing speed of the charging voltage due to different characteristic of the respective accumulator block.
Another object of this invention is to provide an accumulator power supply unit technology in which a combination of electric double layer capacitors and secondary batteries may be used for an accumulator block in series or series-parallel connection as shown in a circuit structure of FIG. 2 in this invention, thereby enabling to independently set the charging electric current and the charging voltage for charging the respective accumulator block
Another object of this invention is to provide an accumulator power supply unit technology which efficiently charges an accumulator block such as electric double layer capacitors and secondary batteries in series or series-parallel connection.
Another object of this invention is to provide an accumulator power supply unit technology which only charges the specific accumulator block in need of charging without affecting the charge of other accumulator blocks when charging an accumulator block such as electric double layer capacitors and secondary batteries in series or series-parallel connection.
In order to resolve the above problems, this invention provides an accumulator power supply unit, comprising plural accumulator blocks in a series connection or a series-parallel connection and plural transform charging circuits connected in parallel with the respective accumulator block, wherein the respective accumulator block is independently charged by the transform charging circuit. Further this invention provides a method for controlling the charge of an accumulator power supply unit, comprising steps of connecting accumulator blocks in series or series-parallel manner, connecting transform charging circuits in parallel to the respective accumulator block, and charging the respective accumulator block independently by the transform charging circuit.